This project is directed toward the definition and understanding of visual capacities and mechanisms in a group of animals having a unique visual adaptation, a cone-dominated retina. So far tests of color vision and visual sensitivity have been completed on five different species of ground-dwelling sciurids. Of great interest is the finding that all of these species possess dichromatic color vision. Future research will involve further studies of these sciurids along several lines; (a) additional species from the family Sciuridae will be examined in behavioral tests to determine if the all-cone adaptation is consistently associated with dichromatic color vision; (b) measurements of spectral saturation and several experiments investigating the effects of chromatic adaptation in the ground squirrel will be conducted; (c) several basic features of spatial vision (resolution, orientation, and movement) will be assessed in behavioral experiments; (d) a series of physiological studies involving unit recording and receptive field characterization will be carried out; and (e) the arboreal squirrel will be studied to determine how its visual capacities and mechanisms relate to those of the ground-dwelling sciurids.